Bug#1035779: linux-image-5.10.0-22: kvm/qemu kernel null pointer dereference, VM doesn't start

From	Salvatore Bonaccorso <carnil@debian.org>
Newsgroups	linux.debian.bugs.dist, linux.debian.kernel
Subject	Bug#1035779: linux-image-5.10.0-22: kvm/qemu kernel null pointer dereference, VM doesn't start
Date	2023-05-10 08:00 +0200
Message-ID	<GtL1L-7Qxj-3@gated-at.bofh.it> (permalink)
References	(2 earlier) <GtBlL-7KxC-5@gated-at.bofh.it> <Gtoyd-7CEJ-1@gated-at.bofh.it> <GtIwW-7P7m-1@gated-at.bofh.it> <Gtoyd-7CEJ-1@gated-at.bofh.it> <GtIwW-7P7m-1@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Cross-posted to 2 groups.

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Hi Jared,

On Wed, May 10, 2023 at 03:13:05AM +0000, Jared Epp wrote:
> Hi Salvatore,
> 
> Thanks for the quick reply!

Thanks to you for your quick testing :)

> > > 
> > > This sounds similar to the
> > > https://forum.proxmox.com/threads/with-latest-5-15-104-1-pve-windows-server-vm-freeze-stuck.125294/
> > > issue. Would you be able to verify two things:
> > > 
> > > Check how the Windows VM is configured and if you pass the
> > > '+hv-tlbflush' flag.
> > > 
> 
> You're right, I am passing this flag. In libvirt I use:
> 
> <domain>
>   <features>
>     <hyperv>
>       <tlbflush state='on'/>
>     </hyperv>
>   </features>
> </domain>
> 
> I tried this fix first and it works. If I reboot into
> 5.10.0-22-amd64, and instead set <tlbflush state='off'/> above, the
> VM boots.

Great, thanks for confirming this temporary workaround.

> > > Additionally, would the attached patch make the issue go away?
> 
> Thanks for the patch; it does fix the issue.  I set this back:
> <tlbflush state='on'/>, applied your patch to 5.10.0-22-amd64 and
> booted my newly patched kernel, and the VM boots.

That's good, thanks for testing. I will ask upstream to cherry-pick
the patch as well for the 5.10.y stable series so it can go in the
next update.

> > 
> > 
> > Now with patch attached.
> > 
> > Regards,
> > Salvatore
> 
> Thanks for your help.  This is my first time using the BTS so I hope
> I've done everything correctly. If there's anything else I should
> do, or if you want me to test something, let me know.

All perfect :)

Regards,
Salvatore

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Bug#1035779: linux-image-5.10.0-22: kvm/qemu kernel null pointer dereference, VM doesn't start Salvatore Bonaccorso <carnil@debian.org> - 2023-05-09 21:40 +0200
  Bug#1035779: linux-image-5.10.0-22: kvm/qemu kernel null pointer dereference, VM doesn't start Jared Epp <jaredepp@pm.me> - 2023-05-10 05:20 +0200
    Bug#1035779: linux-image-5.10.0-22: kvm/qemu kernel null pointer dereference, VM doesn't start Salvatore Bonaccorso <carnil@debian.org> - 2023-05-10 08:00 +0200

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